As this type of steering control apparatus, there is known an apparatus for steering the rear wheels in a reverse phase to the front wheels, in the vehicle equipped with the 4WS mechanism (refer to patent documents 1 and 2).
For example, the patent document 1 discloses a technique in which the rear wheels are transiently steered with respect to the front wheels at the beginning of the turning of the vehicle. For example, the patent document 2 discloses a technique in which a transfer function for controlling the rudder angles of the front and rear wheels are approximated to include only a first-order term with a second-order term removed, thereby simplifying a system.    Patent document 1: Japanese Patent Application Laid Open No. H05-139325    Patent document 2: Japanese Patent Application Laid Open No. H03-67782